After scanning a few books, I might get choosier, that is, either not scanning some books or only scanning a few pages I think I really want (indices, ToCs?). But I have been known to copy hard-to-find books that I had very limited access to (interlibrary loan from several states away). And there was that roleplaying supplement written by a now-deceased World Fantasy Award winner that I photocopied for a friend of his...
I might cut the spines off some of my old magazines and run them through a feed scanner, but the thought of doing that to books squicks me.
If you happen to come across one if those book-slot devices, buy a second one for me.
How long do you think we'll have to wait to see Google or someone else legitimately(?) selling e-access to their scanned library of, say, 1 million+ non-public-domain volumes? Sort of the Rhapsody subscription model, but for books. (I think Safari Books Online is already doing this for a specific niche.)